1. Field of the Invention
The present invention relates generally to a lifter for disk cartridges, such as floppy disks, installed in electronic devices. Particularly, the invention relates to a lifter having a plate spring construction defining a cleaning device for a disk cartridge.
2. Description of the Prior Art
Conventional lifters for a disk cartridge have been disclosed, for example, in U.S. Pat. No. 4,510,546 which describes a structure of a conventional 3.5 inch floppy disk. A structure of a conventional disk lifter will be described hereinbelow with reference to the drawings. A lifter for a disk cartridge is generally faced with a rib to cover a whole area of an effective recording width of the disk. The lifter associates with the rib to lightly press a liner toward the disk surface, dust adhered on the disk surface being wiped off thereby. Referring to FIG. 6, the lifter 101 is composed of a thin plate substrate punched out from sheet stainless steel, for example, so as to have a predetermined configuration. The substrate is folded, or bent, at a predetermined folding angle .theta. along a predetermined fold line 102 to define a fixing member 103 at one side of the fold line 102, for being fixed to an inner surface of the disk cartridge, and a pressing members 104 at the other side of the fold line 102 extending opposite the fixing member 103 for applying lifting pressure to a disk (not shown). When the fixing member 103 is fixed to the inner surface of the cartridge case, the liner is lightly pressed to the disk surface by means of spring force generated by the pressing member 104 extended from the fixing member 103 at the predetermined folding angle .theta..
However, such conventional lifters for disk cartridges, i.e., formed by punching from thin plate stainless steel to a predetermined configuration and being folded at the predetermined angle .theta., present several drawbacks. First, referring again to FIG. 6, pressure applied to the pressing member 104 of the lifter 101 was measured by a pressure sensor 106 at each of six locations (a to f) at distances of 2 m, 7 mm, and 12 mm from the edge of the pressing member for each location. The results of measurement are shown in FIG. 7. As seen in FIG. 7, pressure applied by the lifter fluctuates at each measuring point. Thus, uniform pressure cannot be applied to the disk via the lifter over the whole of the recording track.
Further, a disk cartridge case is comprised of an upper shell and a lower shell, usually formed by injection molding of synthetic resin. A clearance is present within tile cartridge case for accommodating the disk. The size of the clearance depends on the die for molding the casing shells and other molding conditions. The size of the clearance however, affects tile amount of pressure the lifter is able to apply to the disk. Also, clearance variation within tile disk cartridge may occur causing pressure applied by the lifter to vary according to rotation of the disk which further prevents uniform pressure from being applied by the lifter.
FIG. 8 shows measurements taken along the locations a to f at a distance of 7 mm from the edge of the pressing member, under a condition where clearance variation is present in a disk cartridge. As can be seen from the graph, pressure applied by the lifter is difficult to control because tile pressure is greatly varied an becomes unstable when the clearance variation is great.
In order to solve the aforementioned problems, the inventors of the present invention have studied the causes of such problems. FIG. 9 shows a perspective view of the convention lifter, the pressing member 104 of the lifter 101 is bent as shown in FIG. 9, this causes pressure applied thereby to become unstable and gives rise to the above-described problems.
Generally, when a metallic plate is rolled to a thin plate, `curly bend` is generated on the obtained thin plate 107 as shown in FIG. 10. If a lifter is punched from such thin metallic plate 107, bend is present in the surface of the lifter. In addition, when the lifter 101 is formed by folding angle .theta. and the fixing member 108 of the lifter 101 is flattened and fixed to the inner surface of the cartridge case (not shown), distortion generated between the pressing member 104 having a bend in the surface and the fixing member 103 having a flat surface fixed to the cartridge casing becomes concentrated at the fold line 102 which can cause further distortion of the pressing member 104.
Although such bending as shown in FIG. 10 can be straightened to some extent by passing the thin metallic plate 107 through a straightening device, commonly called a leveler, curly bend in the plate surface, caused generally by winding of the plate into rolls during manufacture, as shown in FIG. 11, cannot be easily, or completely removed by such technique.